The present invention relates to a display device which utilizes an emission of electrons into a space that is in a vacuum state, which space is defined between a face substrate and a back substrate; and, more particularly, the invention relates to a display device which has cathode lines having electron emitting sources and control electrodes which control quantity of electrons emitted from the electron emitting sources, and which, at the same time, can exhibit stable display characteristics by maintaining a vacuum in the space between the face substrate and the back substrate.
As a display device which exhibits high brightness and high definition, color cathode ray tubes have been widely used conventionally. However, along with the recent desire for information processing equipment or television broadcasting that is capable of providing images of higher quality, the demand for planar displays (panel displays) which are light in weight and require a small space, while also exhibiting high brightness and high definition, has been increasing.
As typical examples of such panel display devices, liquid crystal display devices, plasma display devices and the like have been developed. More, particularly, as display devices which can provide higher brightness, it is expected that various other kinds of panel-type display devices, including a display device which utilizes an emission of electrons from electron emitting sources into a vacuum (hereinafter referred to as “an electron emission type display device” or “a field emission type display device”) and an organic EL display device, which is characterized by low power consumption, will be put into practice.
Among panel type display devices, such as the above-mentioned field emission type display device, a display device having an electron emission structure which was developed by C. A. Spindt et al, a display device having an electron emission structure of a metal-insulator-metal (MIM) type, a display device having an electron emission structure which utilizes an electron emission phenomenon based on a quantum theory tunneling effect (also referred to as “surface conduction type electron emitting source), and a display device which utilizes an electron emission phenomenon having a diamond film, a graphite film and carbon nanotubes and the like have been known.
One type of field emission type display device includes a back substrate, on which cathode lines having electron-emission-type electron emitting sources and a control electrode are formed on an inner surface thereof, and a face substrate, on which an anode and a fluorescent material are formed on an inner surface that faces the back substrate, wherein both substrates are laminated to each other by inserting a sealing frame between the inner peripheries of both substrates, after which the inside thereof is evacuated. Further, to set the gap between the back substrate and the face substrate to a given value, gap holding members are provided between both substrates.
FIG. 16 is a schematic plan view of a back substrate, which illustrates the constitution of a field emission type display device as viewed from the side of a face substrate (not shown in the drawing). The back substrate 1 is configured such that, on a substrate which is preferably made of glass, alumina or like insulating material, a plurality of cathode lines 2 having electron emitting sources and a plurality of control electrodes of a plate member 4, constituted of a plurality of strip-like electrode elements, are formed. The cathode lines 2 extend in a first direction on the back substrate 1 and are arranged in plural numbers in parallel in a second direction which crosses the first direction. The cathode lines 2 are patterned by printing a conductive paste containing silver or the like, and electron emitting sources are arranged on the surface (face substrate side) of the cathode lines 2. End portions of the cathode lines 2 are extended out to the outside of a frame body 90, which constitutes a sealing frame, as cathode-line lead lines 20, while the opposite end portions thereof extend to terminals 22, which are arranged inside the frame body 90 and outside the display region AR.
On the other hand, the control electrodes 4 are manufactured as separate members and formed on the back substrate 1 at positions to be described later. That is, the control electrodes 4 are arranged close to and above the cathode lines 2 having the electron emitting sources disposed thereon (face substrate side), and, at the same time, they face the cathode lines 2 and are disposed with a given distance therebetween over the whole area of the display region AR. A large number of strip-like electrode elements 41, which constitute the control electrodes 4, extend in the above-mentioned second direction and are juxtaposed in the above-mentioned first direction. The strip-like electrodes 41 have open holes which constitute electron passing apertures at crossing portions thereof aligned with the above-mentioned electron emitting sources on the cathode lines 2. Electrons which are emitted from the electron emitting sources of the cathode lines 2 pass through the electron passing apertures toward the face substrate side (anode side), and pixels are formed over the crossing portions.
The control electrodes 4 are preferably formed such that a thin plate (having a thickness of about 0.05 mm, for example) mainly made of aluminum or iron is formed into a large number of strip-shaped thin plates by etching using a photolithography technique, wherein a large number of electron passing apertures are formed in each strip-shaped thin plate. The control electrodes 4 are fixed to the back substrate 1 by press members 60 or the like that are formed of an insulation body made of glass material at a fixing portion which is arranged outside a display region AR. In the vicinity of the fixing portion or in the vicinity of the frame body 90, lead lines (control-electrode lead lines) 40 are connected to the control electrodes 4 and one end of each of the lead lines 40 extends out to the outer periphery of the display device. Here, it may be possible to use the frame body 90 to perform the function of the press member 60. Then, in response to a potential difference between the cathode lines 2 and the control electrodes 4, an emission quantity (including ON and OFF states) of electrons from the electron emitting sources provided on the cathode lines 2 can be controlled.
On the other hand, the face substrate, which is not shown in the drawing, is formed of an insulation material having light transmissivity, such as glass or the like, and anodes and fluorescent materials are formed on an inner surface thereof. The fluorescent materials are disposed in areas corresponding to the pixels which are formed at the crossing portions between the cathode lines 2 and the control electrodes 4. In the drawing, x indicates the direction of extension of the control electrodes 4, y indicates the direction of extension of the cathode lines 2, and z indicates the direction which is perpendicular to the substrate surfaces of the back substrate and the face substrate.
The back substrate 1 and the face substrate having the above-mentioned constitution are sealed together by way of the frame body 90, and the inside space sealed by the sealing frame 90 is evacuated through an exhaust hole 11 so that a vacuum of 10−5 to 10−7 Torr is created therein, thus forming a field emission type display device. The above-mentioned electron emitting source is constituted of carbon nanotubes (CNT), diamond-like carbons (DLC), other field emission cathode material or other field emission shapes.
Here, as examples of literature which disclose this type of electron emission type display device, except for the constitution of the control electrodes formed of the strip-like electrode elements, reference is made to Japanese Unexamined Patent Publication 1995-326306, Japanese Unexamined Patent Publication 1999-144652, Japanese Unexamined Patent Publication 2000-323078, and Japanese Unexamined Patent Publication 2001-338528.